# Changing Units of Mass

Content Changing Units of Mass
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## Units of Mass

What is Mass? When we measure mass, we are measuring the amount of matter that makes up an object. What are units of mass? Mass must be measured in units of grams and kilograms. In this text you will learn about units of mass and how to convert grams to kilograms and vice versa.

## Units of Mass – Grams and Kilograms

What are grams and kilograms? A gram is one of the units of mass. We use grams to measure smaller objects, like a small seashell. One small seashell weighs about one gram. When we write grams, we can abbreviate using the letter ‘g’.

A kilogram is also one of the units of mass. We use kilograms to measure larger objects, such as a pineapple. One pineapple weighs about one kilogram. When we write kilograms, we can abbreviate using the letters ‘kg’.

Now that we know a little more about the units of weight and mass, let’s learn about converting between kilograms and grams.

## Units of Mass – Conversion

Since we know what units are units of mass, let’s see how we can convert them using a units of mass chart, also known as a ratio table. One kilogram is equal to one thousand grams and one thousand grams is equal to one kilogram.

The table below shows units of mass, grams and kilograms, titled g and kg as these are metric units of mass for short. It also shows how to convert three kilograms into grams. Since one kilogram is equal to one thousand grams, we multiply three kilograms by one thousand to get three thousand grams.

If we want to convert fourteen thousand grams into kilograms, we solve it by using the inverse, or opposite, operation. Fourteen thousand grams divided by one thousand is fourteen kilograms. We now know how many grams and kilograms the objects weigh.

## Units of Mass – Summary

What are the units of mass? Mass must be measured in units of weight, such as grams and kilograms. Converting them is done using a units of mass chart, also known as a ratio table. We can use a ratio table when converting grams and kilograms. We then know the weight of things measured in grams and kilograms.

Kilograms Grams
1 1,000
3 3,000
14 14,000

Want some more units of mass practice? You can find examples, a converting grams and kilograms worksheet, along with other activities, and exercises on our website.

### TranscriptChanging Units of Mass

Zuri and Freddie are scientists for the day. They have their white coats on and are ready to collect data on some marine species. They need our help calculating how much several of them weigh. Before we start, we need to know how to measure grams and kilograms. Matter is anything that has weight or mass and takes up space. When we measure mass, we are measuring the amount of matter that makes up an object. We measure mass in units called grams and kilograms. A gram is a unit used to measure mass. We use grams to measure smaller objects, like a small seashell. When we write grams, we can abbreviate using the letter g. A kilogram is a unit used to measure mass, and is made up of one thousand grams. We use kilograms to measure larger objects, such as this bird, known as a puffin. When we write kilograms, we can abbreviate using the letters kg. When we measure mass with grams and kilograms we use a tool called a scale. There are many different types of scales and you might recognise them from home, school, the doctor's or even the fruit and vegetable section of a shop. Sometimes we need to convert, or change, kilograms to grams and grams to kilograms. One kilogram is equal to one thousand grams and one thousand grams is equal to one kilogram. We can use a ratio table to write our conversions. To set up the ratio table, first label kilograms on one side and grams on the other. One kilogram is one thousand times bigger than one gram. That means to convert kilograms to grams, we multiply by one thousand. Write times one thousand next to the kilogram we are converting and solve. One times one thousand is one thousand, so there are one thousand grams in one kilogram. Let's help Zuri and Freddie convert grams and kilograms so they can record how much each marine species weighs. First, they weigh a Galapagos penguin and record three kilograms. How many grams is three kilograms? Remember, one kilogram is one thousand grams, so we multiply three times one thousand. Three times one thousand is three thousand, so there are three thousand grams in three kilograms. Next, they weigh a sea otter and record fourteen kilograms. How many grams is fourteen kilograms? Fourteen times one thousand is fourteen thousand, so, there are fourteen thousand grams in fourteen kilograms. The last animal they weigh is a sea lion. They record three hundred thousand grams. This time we need to calculate how many kilograms are in three hundred thousand grams by using the inverse or opposite operation. The inverse operation of multiplication is division, so we divide by one thousand. What is three hundred thousand divided by one-thousand? Three hundred, there are three hundred kilograms in three hundred thousand grams. Wow, sea lions have a lot of mass! Remember, a gram is a unit used to measure mass. When we write grams, we can abbreviate using the letter g. Grams are used to measure smaller objects. A kilogram is a unit used to measure mass, and is made up of one thousand grams. When we write kilograms, we can abbreviate using the letters kg. Kilograms are used to measure larger objects. Let's see what Zuri and Freddie are going to do next! Whoa, that's a big whale! How many kilograms do you think it weighs? Write your guesses in the comments!

## Changing Units of Mass exercise

Would you like to apply the knowledge you’ve learnt? You can review and practice it with the tasks for the video Changing Units of Mass.
• ### How much do the animals weigh?

Hints

Try to use a conversion table to help you work out how many grams are in a kilogram.

As we know that there are 1,000 g in a kilogram, we can find $\frac1 2$ kg by halving 1,000.

Solution
• To convert kg into g, we multiply by 1,000.
• The otter is 8 kg. If we multiply this by 1,000 we get 8,000 g.
• The pelican is 7 kg. If we multiply this by 1,000 we get 7,000 g.
• The beaver is 11 kg. If we multiply this by 1,000 we get 11,000 g.
• The water vole is 2 $\mathbf{\frac{1}{2}}$ kg or 2.5 kg. If we multiply this by 1,000 we get 2,500 g.
• ### Missing masses.

Hints

Remember that to convert from kg to g, we multiply by 1,000. So 5 kg = 5,000 g.

To convert from g to kg, we divide by 1,000. So 30,000 g = 30 kg.

We can find half a kilogram by halving 1,000 because 1 kg = 1,000 g.

Solution
• Seashell: $\frac1 2$ kg = 500 g (because 1 kg = 1,000 g and 1,000 $\div$ 2 = 500).
• Puffin: 1$\frac1 2$ kg = 1,500 g (because 1 kg = 1,000 g, $\frac1 2$ kg = 500 g, 1,000 + 500 = 1,500).
• Sea Otter: 15 kg = 15,000 g (because 15 x 1,000 = 15,000).
• Sea Lion: 12,000 g = 12 kg (because 12,000 $\div$ 1,000 = 12).
• Penguin: 50,000 g = 50 kg (because 50,000 $\div$ 1,000 = 50).
• ### Using grams and kilograms.

Hints

0.5 is the same as $\frac1 2$ so 0.5 kg means $\frac1 2$ kg.

Remember that we can convert kg to g by multiplying by 1,000. 3 kg x 1,000 = 3,000 g.

Solution

Here are the correct answers. We know that 0.5 is the same as $\frac1 2$.

• ### What do the animals weigh together?

Hints

Try converting the masses that are in kilograms to grams by multiplying by 1,000. You can move the digits 3 places to the left. For example, 2.630 kg = 2,630 g.

Use the column method to solve the addition problems.

If the total must be 9 kilograms, this means the total in grams must be 9,000.

Solution
• The two animals that total 6 kg are the otter and the duck. 4.2 kg + 1,800 g is the same as 4,200 g + 1,800 g = 6,000 g. 6,000 g = 6 kg.
• The two animals that total 9 kg are the vole and the beaver. 1,160 g + 7.84 kg is the same as 1,160 g + 7,840 g = 9,000 g. 9,000 g = 9 kg.
• The two animals that total 10 kg are the pelican and the goose. 3,560 g + 6,440 g = 10,000 g. 10,000 g = 10kg.
• ### How much does the animal weigh?

Hints

Try making a conversion chart to help you. We know that 1,000 g is equal to 1 kg or 1 kg is equal to 1,000 g.

To convert grams to kilograms we need to divide by 1,000. 5,000 $\div$ 1,000 = 5.

To convert kilograms to grams we need to multiply by 1,000. 5 x 1,000 = 5,000.

Solution
• The animals that weighs 2 kg is the penguin because 2 kg is equal to 2,000 g.
• We know this because 1,000 g = 1 kg.
• We can also multiply by 1,000. 2 x 1,000 = 2,000.
• ### Make the scales balance.

Hints

Could you convert the kg into g to help you solve the problem?

The boxes need to balance, so if there are two boxes on one side, their total mass must equal the other side.

If the totals of two boxes must sum 2 kg, take one of the boxes' mass away from the 2 kg.

Solution
• To find the value of the first scale: 2 kg = 2,000 g, so 2,000 - 1,400 = 600 g.
• To find the value of the second scale: 3 kg = 3,000 g, so 3,000 - 1,850 = 1,150 g.
• To find the value of the third scale: 2 kg = 2,000 g, so 2,000 - 1,050 = 950 g.
• To find the value of the fourth scale: 1 kg = 1,000 g, so 1,000 - 460 = 540 g.