New words：
chalk [tʃɔk]
n.粉笔
v.用粉笔写（或画）
Sample Sentences：
The teacher wrote on the blackboard with a piece of chalk.
She wiped the chalk marks off the blackboard with an eraser.
He chalked a math problem on the blackboard and asked us to solve it.
New words：
unit [ˈjunɪt] n. 单元；单位
Sample Sentences：
The basic unit of length is the metre.
The basic unit of society is the family.
We are studying Unit 5 in the biology textbook.
The team was divided into smaller working units.
New words：
balance [ˈbæləns] n.余额，余数，结存；天平
Sample Sentences：
They were due to pay the balance on delivery.
The chemist measured the powder on a balance.
Don’t forget to check your phone’s data balance.
I'd like to check the balance in my account please.
The balance is a basic tool in physics experiments.
New words：
item [ˈaɪtəm] n.项目；一件商品（或物品）；新闻中的）一则、一条；条款
Sample Sentences：
What's the next item on the agenda?
The store offers free shipping for items over $50.
The lawyer reviewed each item in the agreement.
There was an item about the accident in the news.
New words：
practical [ˈpræktɪk(ə)l] adj.实际的；切实可行的；真实的；客观存在的impractical [ɪmˈpræktɪk(ə)l] adj.不明智的；不现实的；不切实际的
Sample Sentences：
Paul was dreamy and not very practical.
The book provides practical advice for job seekers.
She criticized the impractical plan.
Wearing high heels to climb a mountain is impractical.